Compounds according to formula (I) wherein n is 0-3, R¹ is optionally substituted C_1-6 alkyl, C_2-6 alkenyl, or C_2-6 alkynyl, Heterocycle, Aromatic heterocycle, Aryl or hydrogen and R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are each independently selected from hydrogen and optionally substituted C_1-6 alkyl, or R⁵ and R⁸ are an alkylene chain, are novel. They are useful in the treatment of thrombotic conditions and other pathologies associated with fibrin deposition ##STR1##